Pump



A ril 12, 1966 w. GREGOR 3,245,354

PUMP

Filed June 24, 1963 ti )7 T v a j}, I MOTOR f .I if V I J Q 9 7nvenlor:

WILHELM GREGOR 3 owcun fim g nttomefss United States Patent WilhelmGregor, Hamburg-Hausbruch, Germany, assignor to LicentiaPatent-Verwaltungs-G.m.b.H., Frankfurt am Main, Germany Filed June 24,1963, Ser. No. 289,940 Claims priority, application Germany, June 22,1962,

L 42,286 3 Claims. (Cl. 103-57) The present invention relates generallyto the pump art, and, more particularly, to infinitely variable axialpiston pumps designed to provide maximum output.

In the manufacture of groups of infinitely adjustable multicylinderaxial piston pumps having cylinders which may be tilted and wherein thegroups each have different outputs, the output magnitudes of the unitsof a group with respect to that of other groups had been provided insuch an arrangement that they were successive in accordance with ageometrical or arithmtical'progression, or the stroke volumes of thegroups formed an arithmetical progression.

When such axial piston devices are driven directly by an electric motorhaving a speed of rotation which is determined by the frequency of theelectric mains providing the driving current, they are operated withvarious maximal rates of flow of the pressure fluid. Such rates of flowmany times either do not attain the critical or limit value which ispermissible, or even exceed this critical value. In the first case .thepumps are not fully utilized hydraulically and in the second case theyare no longer properly operable over the entire range through which thecylinders may be tilted.

The main object of the present invention is to provide axial pistonpumps of the above-mentioned type which can be fully utilizedhydraulically when, as is normally the case, their drive is provided byan electric motor having a speed of rotation which is determined by thefrequency of the electric mains.

Another object of the invention is to provide a device of the characterdescribed Which is simple in construction.

These objects and others ancillary thereto are accomplished according topreferred embodiments of the invention wherein the pitch diameter of theball-type hearing of the cylinder pistons is such that a rate of flowwhich is as great as possible, considering the viscosity of the pressurefluid is obtained, and this large flow rate is a maximum rate of flow ofthe axial piston pump and is provided at that time when the drive of thepump is carried out directly by an electric motor having a predeterminedspeed of rotation which is correlated with the frequency of the electricmains providing current to the motor.

In all hydraulic motors, the maximum rate of flow of the operating ordriving medium is given by the viscosity, the form of the channels, andthe low pressure in the suction line. These factors are constant in allpumps of different structural sizes if the conditions are otherwise thesame. The variable factors are the driving speed of rotation and thepitch diameter.

Since the speed of rotation of the electric motors is provided by thefrequency of the mains, the result is that, for example, with a fourpole drive motor the driven hydraulic device must be provided withdouble the pitch diameter as in the case of a two pole drive motor.Furthermore, in an eight pole drive the pitch diameter must be fourtimes as large as that of a two pole drive or twice as large as in thecase of a four pole drive motor.

Additional objects and advantages of the present invention will becomeapparent upon consideration of the following description when taken inconjunction with the accompanying drawing in which the sole figure is aschematic sectional view providing an example of an axial piston pumpconstructed in accordance with the present invention.

When axial piston motors operate using filler pumps, then substantiallyhigh rates of flow can be used. A particular feature of an axial pistonpump according to the present invention is the use of a filler pump. Theoil pressure of the filler pump is such that a rate of flow which is asgreat as possible considering the viscosity of the pressure fluid isattained as a maximum rate of flow of the axial piston pump at the timewhen the drive of the axial piston pump is carried out directly by anelectric motor having a predetermined speed of rotation which iscoordinated with the frequency of the mains providing the electriccurrent.

Such a pump is illustrated in the drawing, and with more particularreference now to the drawing, a drive shaft 1 is supported in a bearingbody 3 and the drive shaft has a drive flange 2. The left front side ofthe bearing body carries the level control which is not shown and bymeans of which the pressure fluid is fed to or carried away from thecylinders 4 through the piston rods 5 which are hollow. At the bottom ofcylinders 4, balls 6 are provided which are mounted in a flange 7 in amanner which allows pivotal motion between the cylinders and the flange.Flange 7 is in turn rotatably mounted on the stationary pivot frame 8.By means of frame 8 the pitch angle a can be adjusted.

The hollow piston rods 5 are supported in drive flange 2 by a type ofball and socket connection to allow pivotal movement. The geometricalposition on which the centers 9 of the balls of the piston rod bearingslie is the pitch diameter 10. In accordance with the present invention,

pitch diameter 10 is so large with a given maximum setting of thetilting angle a that the maximal permissible rate of flow of the axialpiston pump is obtained at a speed of rotation which at leastapproximately corresponds with the rated speed of an electric motorwhose rotational speed is coordinated with the frequency of the mainsproviding the motor with current.

By the use of axial piston pumps of this type, structural groups can bebuilt which, coordinated with the usually used frequency, contain onlypumps which always have only one electric motor as the drive unit and bymeans of which they can always be fully utilized hydraulically andmechanically.

It will be understood that the above description of the presentinvention is susceptible to various modifications, changes, andadaptations, and the same are intended to be comprehended within themeaning and range of equivalents of the appended claims.

The pitch diameter of a variable delivery pump according to theinvention is actually fixed by the speed of the driving motor (frequencyof electric supply) and by the critical Reynolds number which, as isknown, results from its attached factors which, for their parts, resultagain from the construction of the concerning variable delivery pump andfrom the hydraulic medium used as well as from the pressure in thesuction lead. At a viscosity of the hydraulic medium of about degreesEngler, with smooth, cylindrical supply leads, with little resistance,at an open circuit flow and at a tilting angle of degrees, the followingfigures show to be the most favourable values for the pitch diameterfrom a design point of view, e.g. for a frequency of the electric supplyof 50 and 60 c.p.s.

Pitch Diameter 50 cps. Pitch 60 c.p.s. E 'cctric Electric Diameter,

Motor, r.p.n1. Motor, cm.

Cm. Inches r.p.m.

At variable delivery pumps of this design, which work with filling pumpand therefore with prepressure, higher critical Reynolds numbers areapplicable, i.e. higher flow speeds are permissible and consequently thevariable delivery pumps with the before-stated pitch diameters can berun at considerably higher speeds.

However, as the majority of the pumps work without filling pumps it isexpedient to fix the pitch diameter for a design series of thesevariable delivery pumps for open circuit flow.

What is claimed is:

1. A group of related articles of manufacture comprising a series ofinfinitely adjustable axial piston pump devices having similarparameters and each having drive means including a drive shaft and anelectric motor each having a predetermined speed of rotation differentthan the other and which is coordinated with the frequency of the mainsproviding current thereto; and driven means connected to be rotated bysaid drive means and including (a) a member connected to and coaxialwith said drive shaft, (b) a plurality of pistons, pivotally mounted tosaid member, (c) a plurality of cylinders parallel to each other and inaxial symmetry to each other in which said pistons are operable, and

l (d) a cylinder holding element to which said cylinders are connected,said cylinder holding element being pivotally mounted with respect tosaid member so that the axes of the member and of the element can definean angle therebetween, the pitch diameter of said pistons beingdependent upon the speed of said motor such that a rate of flow which isas great as possible is reached considering the viscosity of thepressure fluid as the maximum rate of fiow of the axial piston pump atthe time when the drive is carried out directly by said electric motor.2. The group defined in claim 1 wherein said motor speed in r.p.m. andsaid pitch diameter in cm. is related as follows:

R.p.m.: Pitch diameter (cm.) 3600 2.5 3000 3.0 1800 5.0 1500 6.0 12007.5 1000 9.0 900 750 12 0 600 l5 0 500 18 0 450 20.0 375 25.0 360 25.0300 30.0

3. The group as defined in claim 2 wherein the related motor speeds andpitch diameters are considered at a viscosity of the hydraulic medium ofabout 5 degrees Engler, with smooth, cylindrical supply lines havinglittle resistance at an open circuit flow and at a tilting angle of 20degrees.

References Cited by the Examiner UNITED STATES PATENTS 2,146,133 2/1939Tweedale 103-162 3,040,672 6/1962 =Foerster et al. 103162 3,066,60912/1962 Hann 103-5 ROBERT M. WALKER, Primary Examiner.

1. A GROUP OF RELATED ARTICLES OF MANUFACTURE COMPRISING A SERIES OFINFINITELY ADJUSTABLE AXIAL PISTON PUMP DEVICES HAVING SIMILARPARAMETERS AND EACH HAVING DRIVE MEANS INCLUDING A DRIVE SHAFT AND ANELECTRIC MOTOR EACH HAVING A PREDETERMINED SPEED OF ROTATION DIFFERENTTHAN THE OTHER AND WHICH IS COORDINATED WITH THE FREQUENCY OF THE MAINSPROVIDING CURRENT THERETO; AND DRIVEN MEANS CONNECTED TO BE ROTATED BYSAID DRIVEN MEANS AND INCLUDING (A) A MEMBER CONNECTED TO AND COAXIALWITH SAID DRIVE SHAFT, (B) A PLURALITY OF PISTONS, PIVOTALLY MOUNTED TOSAID MEMBER, (C) A PLURALITY OF CYLINDERS PARALLEL TO EACH OTHER AND INAXIAL SYMMETRY TO EACH OTHER IN WHICH SAID PISTONS ARE OPERABLE, AND (D)A CYLINDER HOLDING ELEMENT TO WHICH SAID CYLINDERS ARE CONNECTED, SAIDCYLINDER HOLDING ELEMENT BEING PIVOTALLY MOUNTED WITH RESPECT TO SAIDMEMBERS TO THAT THE AXES OF THE MEMBER AND OF THE ELEMENT CAN DEFINE ANANGLE THEREBETWEEN, THE PITCH DIAMETER OF SAID PISTONS BEING DEPENDENTUPON THE SPEED OF SAID MOTOR SUCH THAT A RATE OF FLOW WHICH IS AS GREATAS POSSIBLE IS REACHED CONSIDERING THE VISCOSITY OF PRESSURE FLUID ASTHE MAXIMUM RATE OF FLOW OF THE AXIAL PISTON PUMP AT THE TIME WHEN THEDRIVE IS CARRIED OUT DIRECTTLY BY SAID ELECTRIC MOTOR.